Approaching the Delay-Limited OFDM Broadcast Capacity with OFDMA

Recently, in a companion paper we introduced the delay-limited capacity (DLC) region of an orthogonal frequency division multiplexing (OFDM) broadcast channel (BC). The DLC region is of utmost interest, since it e.g. provides an ultimate performance limit for all minimum sum power algorithms with given rate requirements. In this work we use the principle of rate water-filling to derive bounds on the OFDM DLC based on order statistics. We enhance these results to develop analytical lower bounds on the OFDM BC DLC region. The bounds are based on frequency division multiple access (FDMA) and ordinal channel state information (CSI), suggesting suboptimal but simple resource allocation schemes. Finally, these schemes are compared to a new algorithm using full CSI. Every practical sum power minimization algorithm using FDMA has to compete with these lower and upper bounds